1. Field of the Invention
The invention in general relates to miniature switches and more particularly to a switch useful in microelectromechanical systems.
2. Description of Related Art
A variety of devices exist for controlling propagation of signals in DC as well as RF circuits. For example, electronic RF switches in common use include the gallium arsenide (GaAs) field effect transistor (FET) and the GaAs pin diode. Both of these devices operate at extremely high speeds and can achieve switching rates measurable in nanoseconds.
For some applications however, the GaAs FET has an objectionably high resistance when closed and a relatively low cut-off frequency, for example, 600 GHz. The pin diode exhibits a higher cut-off frequency of around 2 THz, however it, along with the GaAs FET, exhibits an objectionably high capacitance in the off state. For this reason these RF switches are usually operated with a separate shunt inductor resonant with the capacitance, at the operating frequency.
This added inductor advantageously increases the impedance of the switch in the off condition, however this arrangement objectionably lowers the operating bandwidth of the overall switch device.
With the present invention, the electromechanical mercury wetted switch operates at a slower speed than the all electronic variety, however the switching rate, measurable in microseconds, is still more than adequate for many intended purposes.
Further, the switch of the present invention has a significantly lower capacitance in the off state and has a lower resistance in the on state of operation resulting in a cut-off frequency of several hundred THz.